I need to build a system to control lights using line-level audio signal.

My idea is to acquire the signal from my mixer using a microcontroller (or FPGA), apply some filters and finally drive 5 leds totem (columns, whatever is a cylinder with leds sticked on it...) few meters away from the control unit using arduino (or a general lowcost micro) and power mosfets. I'd like to control each totem individually and cascade them (fewer cables around).

Since I only need to send a light-on/off command on the bus I don't need a fully fledged I2C communication: just a basic one, the standard 100KHz would be way more than enough. But I need to use a wire of several meters (let's say 10 or 20).

  • Would a standard I2C work?
  • Should I use DMX or I2C?

I know DMX is the standard in this applications, but I'd like I2C the most for the following reasons:

  • Since this is for University (not targeted at market) I think is more "educational"
  • I could update the project using fpga and then I could use an I2C enabled ADC and don't have to write the code for DMX.

What do you think? Any suggestion is highly appreciated and I hope I didn't miss something obvious.

Thanks in advance, Andrea

  • \$\begingroup\$ No need to reinvent the wheel but it you want it addressable RGB there are chips for this on stripleds or you can make it discrete in many ways. I2C works fine with R pullup and cable capacitance limiting rise time. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 3 '17 at 16:18
  • \$\begingroup\$ Thanks for the fast reply. For now, I just need to address 5 items not each LED. I now the RC time constant will rise a lot if I use longer cables, but I think my max data rate to a single node would be something to achieve on/off light switch at no more than 50Hz... So I expect the I2C to work reasonably good.. Am I right? \$\endgroup\$ – a_bet Oct 3 '17 at 16:24
  • \$\begingroup\$ I think that doing this personal project using DMX would be more "educational". DMX is an industry standard lighting protocol and being able to say in your resume that you've implemented it successfully (even though it's not complicated) may be worth something. Doing RDM on top of it would probably be excessive (although more impressive...) \$\endgroup\$ – brhans Oct 3 '17 at 17:10
  • \$\begingroup\$ And doing S-ACN would be downright overkill (It usually is). Personally I would go for DMX or at least something over RS485 (At which point it may as well be DMX), because I2C really does not do well over long cables, it might sort of work until someone fires up an electric drill in the vicinity (Or the fridge compressor starts, or someone gets a cell phone call, or...). \$\endgroup\$ – Dan Mills Oct 3 '17 at 17:21
  • \$\begingroup\$ Thanks for your kind replies. I'm considering DMX then because it would be nice to see the final result in action (coupled with some serious amp and speakers). \$\endgroup\$ – a_bet Oct 3 '17 at 17:59

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